The present invention relates to controlling the temperature of an electronic engine control unit (ECU).
The primary function performed by ECU units in internal combustion engines is to regulate the fuel supply to the engine cylinders but they are sometimes additionally used to perform other function and to control ancillary equipment such as an engine brake, an alternator or an air compressor. Controlling of any components typically results in higher heat dissipation from the ECU.
Overheating is a common cause for the failure of the ECU. This applies particularly to agricultural tractor and heavy duty highway truck engines which are required to operate under widely differing ambient conditions. For this reason, it is known to cool the ECU of such engines by mounting it on a cooler through which flows the fuel being supplied to the engine cylinders.
Hitherto, the ECU cooling system has been designed to cope with certain specified extremes of ambient temperature and engine load but if the engine is operated outside the specified operating range then failure of the ECU could occur. After such a failure, the engine could in some cases operate in a xe2x80x9climp homexe2x80x9d mode but it could not be used efficiently.
With a view to overcoming the foregoing disadvantages, the present invention provides an engine having an electronic engine control unit (ECU) and a temperature management system for the ECU to prevent failure of the ECU through overheating, the temperature management system comprising means for monitoring or evaluating the temperature of the ECU to determine when the temperature of the ECU is approaching a predetermined limit and means for limiting further heating of the ECU to prevent the said limit from being exceeded.
The invention is based on predicting danger of failure of the ECU as a result of overheating and taking action to prevent such failure before an excessive temperature is reached.
The prevailing temperature of the ECU can be measured directly, for example by a temperature sensor in contact with the ECU, or indirectly, for example by measuring the temperature of the coolant flowing through a cooler in contact with the ECU. Alternatively, means may be provided for measuring the temperature of ambient air and of any cooling medium serving to cool the ECU and evaluating from the measured temperatures the maximum rate of power dissipation in the ECU. Once it has been ascertained by measurement or evaluation that the temperature of the ECU is approaching (but has not yet reached) the point where there is a risk of failure through overheating, steps are taken to limit any further temperature rise.
The temperature rise of the ECU is determined by two factors, namely the amount of heat generated by the ECU and the amount of heat removed from the ECU. Either or both of these factors can be modified when it has been determined that a risk of overheating is imminent.
To improve the cooling of the ECU, it is possible to switch on a fan, increase the rate of coolant flow, or alter the temperature of the thermostat in the engine cooling system. To reduce the rate of heat generation within the ECU, it is possible to reduce the maximum engine load, or switch off ancillary equipment.